The present invention relates to a new thermosetting compound and its production method. More particularly, it relates to an esterimide oligomer having excellent heat resistance and also having an appropriate reactivity for lamination and molding, and a production method thereof.
Thermosetting resins have been used for various kinds of electric insulation materials and structural materials for cast molding, impregnation, lamination and molding. Recently, conditions in these usages have become increasingly more severe. Especially, the heat resistance of the materials has become an important property. Formerly, for such usage, a thermosetting polyimide resin or a heat-resistant epoxy resin has been used. Among them, as the thermosetting polyimide resin, "Kerimid" (trade name, manufactured by Rhone-Poulenc Chemie) mainly composed of a bismaleimide compound and diaminodiphenylmethane is used (Matsuo Fujisawa, Plastics, Vol. 34, No. 7, page 75, 1983). However, the thermosetting polyimide resin has a disadvantage of needing a high temperature and a long heating time during forming. In addition, as diaminodiphenylmethane is harmful to a human body, there is a problem of sanitation in handling. In addition, recently, an acetylene terminated type polyimide has been put on the market as "Thermid" (trade name, manufactured by Gulf R&D, Japanese Laid-Open Publication No. 53-119865). However, because its organic solvent solubility is comparatively low, high boiling point polar organic solvents such as dimethylformamide and dimethylacetamide must be used, and thus, there is a problem in handling.
In order to solve the problem encountered with the polyimide, numerous improvement methods have been proposed for the resin, and among them, various kinds of polyesterimide resin have been proposed from viewpoints of molding property (for example, U.S. Pat. Nos. 4,757,118, 4,362,861, 3,852,246 or Japanese Laid-Open Publication No. 1-123819).
However, it is pointed out that generally, the polyesterimide is lower in softening point and more excellent in resin flowing property than the polyimide, but inferior in heat resistance to the polyimide [Keisuke Kurita et al., Polymer Applications, Vol. 37, No. 2, pgs. 22-26, (1989)].
A new acid dianhydride with ester bonding was at first synthesized using trimellitic acid anhydride as a starting monomer and paratoluenesulfonic acid chloride/pyridine as a reaction solvent, then polyesterimide is synthesized in the same reaction system by introducing diamine therein [H. Tanaka et al., Proceedings/Abstracts of Third International Conference on Polyimides, pgs. 65-68, (1988)]. However, there is no knowledge at all about thermosetting polyesterimides or their reactivity such as photo-reactivity.